Fast magnetic reconnection, believed to be a mechanism for rearranging the magnetic topology and creating energetic particles in many astrophysical and laboratory plasmas, is investigated with the nonlinear gyrokinetic code Gene. After some code-code benchmarking, extensive linear studies are presented, covering all relevant parameter dependencies of two-dimensional slab reconnection. The results are used to ascertain the validity of a fluid model and understand for which parameters it fails to describe the physics correctly. The nonlinear phase is studied for two scenarios: decaying and driven turbulence. In the former case, the initially injected energy is cascading towards the largest scales of the system, whereas a fully turbulent, quasi-stationary state develops if the system is driven through a Krook-type term in the gyrokinetic Vlasov equation.